Bacillus subtilis is a Gram-positive, catalase-positive bacterium commonly found in soil. Members of the genus Bacillus have the ability to form tough, protective endospores, a characteristic which allows the spores of the organism to tolerate extreme environmental conditions, to be heat resistant, and to quantitatively survive lengthy exposure to a wide range of temperatures including freezing and boiling, without loss of viability.
B. subtilis has a long safety record as a food component and as a probiotic, e.g., used in microbial feed supplements to improve intestinal microbial balance by competitively excluding pathogens both in animals and humans. Other Bacillus species are well-known biological insecticidal agents, e.g., Bacillus thuringiensis (Dipel®) is used to combat gypsy moths without harm to other wildlife. Bacillus natto includes food-grade strains mainly used for the fermentation of soybeans, which fermentation process eventually results in a cheap and nutritious food that is rich in amino acids. In fact the term “natto” refers to a Japanese soybean fermented product “Natto”, which is a widely used commercial product.
Bacilli have been studied extensively by researchers and as a result this family includes species with well-characterized genetic and physiological systems. B. subtilis has become a model organism for Gram-positive bacteria, and numerous studies have been published involving manipulation of its genetic structure and regulation of expression of its proteins.
There remains a need for vaccines that are easily produced in large quantities and at low cost to prevent and control emerging viral epidemic and epizootic diseases. Vaccines based on bacterial production systems that can be stabilized for use in tropical areas and under other conditions to minimize loss of activity in areas having minimal storage capabilities are available.